This disclosure relates to saving energy supplied to a clothes dryer, and more particularly relates to methods to improve clothes dryer energy usage while preferably using the same components or hardware found in typical commercially available clothes dryers and also to novel apparatus for enhancing dryer efficiency. It will be appreciated that the disclosure may also find application in a combination washer/dryer apparatus, or by selectively using one or various ones of the different features to be described below.
Appliances for drying articles such as clothes dryers are generally known in the art. Various ways of using heat energy for drying wet clothes in a clothes dryer are also known. For example, a user or consumer may set a predetermined drying time for drying the clothes. This requires the user to estimate the drying time and generally results in the clothing articles being over-heated or under-heated. Selection of an unnecessarily long drying time results in over-heating the clothing articles, higher energy consumption, and the potential for damaging the clothes. Selection of too short a drying time results in the user needing to select a new drying time and subsequently monitor the dryness of the clothes through one or more additional drying periods.
Other models of clothes dryers employ sensors and associated controllers that receive sensor signals and predict a moisture content and degree of dryness in the articles. For example, a temperature sensor or humidity sensor provides appropriate signals to the controller and in response to the input data, the controller predicts a percentage of moisture content and a degree of dryness of the clothing articles. Commonly-owned U.S. Pat. No. 5,899,005 is generally representative of such a clothes dryer and associated process.
Another clothes dryer and associated method stores historical data in a memory. An initial drying time estimate is calculated, and the final time estimate re-calculated based on input time and moisture parameters from one or more sensors, which are then periodically compared to the estimates stored in the memory until such time as the drying cycle is terminated. For example, U.S. Pat. No. 7,478,486 is also commonly-owned by the assignee of the present application and representative of such an arrangement.
There is an ever-increasing desire to save energy in association with operating appliances and particularly for a clothes dryer. The clothes dryers at present are able to give complete drying performance with the help of various sensors and controls as noted above. However, by design both airflow rate and drum inlet air temperature are maintained constant. As a result, the supply of energy can be either more or less than actually required depending on different stages of the clothes drying process. Energy savings in known units is typically achieved by regulating the supply to the heater or by not allowing the clothes to over-heat with the assistance of controls and sensors. However, the goal of known arrangements is slightly different, i.e., to achieve complete drying without any clothing over-heat. These arrangements, however, are not believed to sufficiently save energy and there is a perceived need for improvement.
Thus, a need exists for obtaining similar drying performance with less energy consumption, and preferably using many of the same components or hardware to achieve these goals.